18-01-2013, 04:44 PM
HYDRAULIC OPERATED V TYPE BENDING MACHINE
1HYDRAULIC OPERATED.doc (Size: 1.21 MB / Downloads: 216)
INTRODUCTION
A Hydraulic cylinder (also called a linear hydraulic motor) is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke. It has many applications, notably in engineering vehicles, industrial application, civil applications.
Hydraulic cylinders get their power from pressurized hydraulic fluid, which is typically oil, air. The hydraulic cylinder consists of a cylinder barrel, in which a piston connected to a piston rod moves back and forth. The barrel is closed on one end by the cylinder bottom (also called the cap) and the other end by the cylinder head (also called the gland) where the piston rod comes out of the cylinder. The piston has sliding rings and seals. The piston divides the inside of the cylinder into two chambers, the bottom chamber (cap end) and the piston rod side chamber (rod end / head end).
Flanges, trunnions, clevises, Lugs are common cylinder mounting options. The piston rod also has mounting attachments to connect the cylinder to the object or machine component that it is pushing / pulling. A hydraulic cylinder is the actuator or "motor" side of this system. The "generator" side of the hydraulic system is the hydraulic pump which brings in a fixed or regulated flow of oil to the hydraulic cylinder, to move the piston. The piston pushes the oil in the other chamber back to the reservoir.
Parts of a hydraulic cylinder
A hydraulic cylinder consists of the following parts:
Cylinder barrel
The main function of cylinder body is to hold cylinder pressure. The cylinder barrel is mostly made from a seamless tube. The cylinder barrel is ground and/or honed internally with a typical surface finish of 4 to 16 micro inch. Normally hoop stresses are calculated to optimize the barrel size.
Cylinder base or cap
The main function of cap is to enclose the pressure chamber one end. The cap is connected to the body by means of welding, threading, bolts, tie rod. Cap also perform as a cylinder mounting components. Cap size determined based on the bending stress.
Cylinder head
The main function of head is to enclose the pressure chamber from other end. Head contains an integrated rod sealing arrangement or option to accept a seal gland. The head is connected to the body by means of threading, bolts, tie rod. A static seal / o-ring used in between head and barrel.
Piston
The main function of piston is to separate pressure zone in side barrel. The piston is machined with grooves to fit elastomeric or metal seals and bearing elements. These seals can be single acting or double acting. This difference in pressure between the two sides of the piston causes the cylinder to extend and retract. Piston is attached with the piston rod by means of threads, bolts, nuts to transfer the linear motion.
Piston rod
The piston rod is typically a hard chrome-plated piece of cold-rolled steel which attaches to the piston and extends from the cylinder through the rod-end head. In double rod-end cylinders, the actuator has a rod extending from both sides of the piston and out both ends of the barrel. The piston rod connects the hydraulic actuator to the machine component doing the work. This connection can be in the form of a machine thread or a mounting attachment.
Seal gland
The cylinder head is fitted with seals to prevent the pressurized oil from leaking past the interface between the rod and the head. This area is called the seal gland. The advantage of seal gland is easy removal and seal replacement. The seal gland contains primary seal, secondary seal / buffer seal, bearing elements, wiper / scraper and static seal. In some cases, especially in small hydraulic cylinders, the rod gland and the bearing elements are made from a single integral machined part.
Seals
The seals are considered / design as per the cylinder working pressure, cylinder speed, operating temperature, working medium and application. Piston seals are dynamic seals, can be single acting or double acting. Generally speaking, Elastomers seals made from nitrile rubber, Polyurethane or other materials are best in lower temperature environments, while seals made of Fluorocarbon Viton are better for higher temperatures. Metallic seals are also available commonly used cast iron for seal material. Rod seal are dynamic seals and generally single acting.
The compounds of rod seals are nitrile rubber, Polyurethane, Fluorocarbon Viton. Wiper / scraper are used to eliminates contaminants such as moisture, dirt, and dust, which can cause extensive damage to cylinder walls, rods, seals and other components. The common compound for wiper is polyurethane. Metallic scraper are used for sub zero temperature application, application where foreign material can deposit on rod. The bearing element / wear bands are use to eliminate metal to metal contact. The wear bands are design as per the side load requirements. The primary compounds for wear bands are filled PTFE, Woven fabric reinforced polyester resin, bronze.
USES OF HYDRAULIC BENDING MACHINE
Our range of Hydraulic Breading Machine is used for selectively dispensing flour breading or free flowing breading onto a food product wherein the machine has a frame and conveyor structure supported on the frame defining a conveyance path having a product inlet end and a product outlet end. This machine also comes with a breading hopper attached to the frame adjacent to the inlet end for applying a coating of breading to the food product and also a breading pumping slot structure attached to the frame for providing breading to the input end of the conveyor with a fluffier mechanism mounted on the pumping slot structure to break up any caking or lumping of the breading on the conveyor prior to the point of introduction of the food product to the conveyor.
The Mechanical Screw jacks have been replaced with hydraulically operated jacks. This reduces requirement of man power upto 40% and the Roll bending cycle time is reduced by 40%. The Machine has a capacity to pre bend but with a flat edge of 40% of Top Roll Dia of the machine. It is not out of place to highlight that the pre bend capacity of a given Plate Bending machine is approximately 80% of its roll bending capacity, i.e, A plate bending machine having a capacity of 16 mm thick is capable of Pre bending plates upto 12 mm thickness when equipped with hydraulically operated jacks.
Principles of Hydraulic Drive
Pascal's law is the basis of hydraulic drive systems. As the pressure in the system is the same, the force that the fluid gives to the surroundings is therefore equal to pressure × area. In such a way, a small piston feels a small force and a large piston feels a large force.
The same principle applies for a hydraulic pump with a small swept volume that asks for a small torque, combined with a hydraulic motor with a large swept volume that gives a large torque. In such a way a transmission with a certain ratio can be built.
Most hydraulic drive systems make use of hydraulic cylinders. Here the same principle is used — a small torque can be transmitted in to a large force.By throttling the fluid between the generator part and the motor part, or by using hydraulic pumps and/or motors with adjustable swept volume, the ratio of the transmission can be changed easily. In case throttling is used, the efficiency of the transmission is limited. In case adjustable pumps and motors are used, the efficiency, however, is very large. In fact, up to around 1980, a hydraulic drive system had hardly any competition from other adjustable drive systems.